Combating weeds with o-acyl-3 5-dialkyl-4-hydroxybenzaldoximes

ABSTRACT

2-R,4-(X-COO-N=C-),6-R&#39;&#39;-PHENOL   IN A VARIETY OF CROPS, INCLUDING BROAD-LEAF SPECIES SUCH AS TOMATOES AND SOYBEANS, AS WELL AS CORN AND SMALL GRAINS, PARTICULARLY RICE AND WHEAT, CONTROL OF NOXIOUS GRASSES, INCLUDING CRABGRASS, WILD OATS, FOXTAIL AND SHATTERCANE IS OBTAINED BY PREEMERGENT APPLICATION OF COMPOUNDS HAVING THE STRUCTURAL FORMULA IN WHICH R AND R&#39;&#39; ARE NON-PRIMARY ALKYL OR CYCLOALKYL SUBSTITUENTS HAVING AT LEAST 3 CARBON ATOMS AND X IS AN ELECTRONEGATIVE SUBSTITUENT, FOR EXAMPLE, DICHLOROMETHYL, OR AN UNSATURATED HYDROCARBON STRUCTURE SUCH AS PHENYL OR CYCLOPROPYL.

United States Patent 3,644,524 COMBATING WEEDS WITH 0-ACYL-3,5-DIALKYL-4-HYDROXYBENZALDOXIMES Roger P. Cahoy, Merriam, Kans., assignor to GulfResearch & Development Company, Pittsburgh, Pa.

No Drawing. Original application Nov. 30, 1967, Ser. No. 686,809, nowPatent No. 3,503,732, dated Mar. 31, 1970. Divided and this applicationAug. 19, 1969, Ser.

Int. Cl. C07c 131/00 US. Cl. 260-566 AE 2 Claims ABSTRACT OF THEDISCLOSURE In a variety of crops, including broad-leaf species such astomatoes and soybeans, as well as corn and small grains, particularlyrice and wheat, control of noxious grasses, including crabgrass, wildoats, foxtail and shattercane is obtained by preemergent application ofcompounds having the structural formula in which R .and R arenon-primary alkyl or cycloalkyl substituents havingat least 3 carbonatoms and X is an electronegative substituent, for example,dichloromethyl, or an unsaturated hydrocarbon structure such as phenylor cyclopropyl.

This is a division of co-pending application Ser. No. 686,809, filedNov. 30, 1967, HOW Pat. No. 3,503,732.

DESCRIPTION OF INVENTION Chemical methods of combating weeds are of twogeneral types; those in which a weed control agent is applied before theemergence of the weeds from the soil and those in which the chemical isapplied after emergence of the weeds. By use of a herbicide of theproper selectivity, either method may be used either before or afteremergence of the crop plants. In general, more efficient use of plantnutrients and better yields of crops are obtained if the weeds arekilled either before emergence or shortly thereafter. For some or themore sensitive crops such as soybeans and tomatoes, however, it isdiflicult to use an effective amount of herbicide without severe injuryto the crop and consequent loss of yield. This is particularly true whenan effort is made to control some of the noxious grasses such asshattercane and giant foxtail.

I have discovered a relatively small group of herbicides which may beused for preemergent control of noxious grasses and when used inefifective amounts in this manner, appear to have no significantpost-emergent activity. These compounds are therefore particularlyuseful for pre-emergent weed control in standing crops.

The effective compounds of this invention are O-arylsubstitutedbenzaldoximes having the structural formula in which R and R arenon-primary aliphatic hydrocarbon substituents having at least 3 carbonatoms and X is an electronegative substituent group.

The selection of the electronegative substituent group is of criticalimportance with respect to the phytotoxic properties. When R and R, forexample are both tertiary butyl, and X is methyl or chloromethyl, thesecomposi- 3,644,524 Patented Feb. 22, 1972 tions are particularly usefulfor pre-emergent control of crabgrass in freshly seeded lawns. If X iscyclopropyl or phenyl, a greater variety of grasses may be controlled bypre-emergent treatment, including wild oats and brome grass, in thepresence of either freshly planted or standing crops of soybeans,cotton, wheat and corn. When X is dichloromethyl, this composition, whenused in suitable quantities effects pre-emergence control of crabgrass,wild oats, brome, barnyard grass, pigweed, green foxtail, giant foxtailand shattercane without significant injury to either standing crops orfreshly planted wheat, rice, soybeans, corn, grain sorghum or tomatoes.The weed control compositions of this invention are particularly suitedto modern intensive agricultural techniques in which large plantpopulations are employed and it is not feasible to cultivatemechanically between planting and harvest. The weed control agents ofthis invention may be readily manufactured by suitable modifications ofthe procedures presented for illustrative purposes below.

PREPARATION OF WEED CONTROL AGENTS The3,5-di-tert.butyl-4-hydroxybenzaldehyde and3,5-ditert.butyl-4-hydroxybenzaldoxime, in general, may be prepared bythe method of L. Cohen, J. Org. Chem., 22, 1334 (1957) as illustrated bythe following procedure:

(A) Preparation of 3,S-di-tert.butyl-4-hydroxybenzaldehyde A two literround-bottomed flask was charged with g. (0.36 mole) of2,6-di-tert.butyl-4-methylphen0l, 900 ml. of glacial acetic acid and 200ml. of water. With mechanical stirring, the mixture was warmed to 50 C.to facilitate solution of the phenol. The solution was cooled to 20".Two equivalents of bromine (37 ml.) was added dropwise to the stirredreaction mixture over a period of two hours. Stirring was continued foran additional hour and the reaction mixture was poured into 500 ml. ofice water. The suspension was cooled in an ice bath and the light yellowproduct was collected on a vacuum filter. The filter cake was washedwith dilute acetic acid, followed With several water washings. The crudeproduct was dissolved in one liter of ethanol. While being cooled in anice bath, the addition of 150 ml. of water precipitated the compound.The dried product weighed 47.2 g. (56% yield) and melted at 188-190 C.

(B) Preparation of 3,S-di-tert.butyl-4-hydroxybenzaldoxime A solution of8.3 g. (0.12 mole) of hydroxylamine hydrochloride and 10 m1. of waterwas added to 23.4 g. (0.10 mole) of3,S-di-tert.butyl-4-hydroxybenzaldehyde dissolved in 400 ml. ofmethanol. After adding 4.8 g. (0.12 mole) of sodium hydroxide dissolvedin 8 ml. of water, the reaction solution was warmed at 50 C. for fiveminutes. Some solid material was noted in the reaction flask afterallowing the solution to stand 2.5 hours at ambient temperature. Thesuspension was treated with an equal volume of water, cooled and theproduct was collected on a vacuum filter. The vacuum dried oxime weighed22.9 g. (92% yield) M.P. l2830 C.

(C) Preparation of o-dichloroacetyl-3,5-di-tert.bu-tyl-4-hydroxybenzaldoxime A solution of 7.0 g. (0.028 mole)3,5-di-tert.butyl-4- hydroxybenzaldoxime, 13,5 'g. (0.056 mole) ofdichloroacetic anhydride and ml. of glacial acetic acid was stirred at25-35 for thirty minutes. The yellow solution was poured into 500 ml. ofice Water. A yellow oil separated which rapidly crystallized. Thecollected solid was washed with water, dissolved in benzene and driedover sodium sulfate. The drying agent was removed and most of thebenzene was evaporated. The residual oil was dissolved in hexane.Crystallization yielded 7.5 g. of O- dichloroacetyl 3,5 di tert.butyl 4hydroxybenzaldoxime, M.P. 109-10.

Analysis.-Calculated for C H Cl NO (percent): C, 56.68; H, 6.43; Cl,19.68; N, 3.89. Found (percent): C, 55.57; H, 6.34; CI, 20.10; N, 4.10.

The following compounds are also prepared by essentially the same asillustrated above, by employing the appropriate acyl halide or acidanhydride.

PRE-EMERGENT WEED CONTROL The weed control chemicals exemplified abovewere sprayed on soil in which there was planted seeds of crabgrass,oats, brome grass, wheat, rice, barnyard grass, pigweed, soybeans, greenfoxtail, giant foxtail shattercane and corn. The Weed control agentswere also sprayed on standing millet, soybean, cotton, alfalfa, oats,corn, fiax, radish, sugar beet, Wheat, grain sorghum and tomato plantsat an application rate of lb. per acre, to test for injuriouspost-emergent elfects. The spray mixtures were prepared in the customarymanner, by making up a dispersible concentrate or wettable powderemploying commercial solvents, emulsifiers and dispersing agents whichare available and recommended for use in manufacturing pesticideformulations. The spray mixtures employed in the tests described hereinwere made according to essentially the same procedures and formulationsas those disclosed in U.S. Pat. 3,277,107. The results are summarized inthe following examples.

EXAMPLE 1 At an application rate of 4 lb. per acre, O-chloroacetyl- 3,5ditert.butyl 4 hydroxybenzaldoxime gave substantially completepre-embergent control of crabgrass without significant injury to theseeds of wheat, rice, soybeans or corn. There was no significantpost-emergent effect on any of the standing crops at an application rateof 5 lb. per acre.

EXAMPLE 2 At an application rate of 2 lb. per acre,O-cyclopropanecarbonyl 3,5 ditert.butyl 4 hydroxybenzaldoxime gavesubstantially complete preemergent control of crabgrass, wild oats andbrome grass without significant injury 4, to seeds of wheat, rice,soybeans or corn. There was no significant post-emergent effect in anyof the standing crops at an application rate of 5 lbs. per acre.

EXAMPLE 3 At an application rate-of 2 lb. per acre, O-benzoyl-3,5-ditert.butyl-4-hydroxybenzaldoxime gave substantial completepre-emergent control of crabgrass, wild eat and bronie grass and betterthan 50 percent control of giant fox-tail and shattercane withoutsignificant injury to seeds of wheat, rice, soybeans or corn. At apre-emergent application rate of 10 lb. per acre there was significantinjury to corn seeds, as well as to alfalfa, flax and sugar beet seeds.There was no significant post-emergent effect on any of the standingcrops at an application rate of 5 lb. per acre.

EXAMPLE 4' At an application rate of 2 lb. per acre,O-dichloroacetyl-3,5-ditert.butyl-4-hydroxybenzaldoxime gave substantially complete pre-emergent control of crabgrass, wild oats, bromegrass, pigweed, giant foxtail and shattercane and better than 50 percentcontrol of barnyard grass and green foxtail, without significant injuryto rice, soybeans or corn seeds. There was slight injury to wheat, forwhich compensation is possible by planting thicker. There Was nosignificant post-emergent effect on any of the standing crops at anapplication rate of 5 lb. per acre.

The above illustrative examples show the unique characteristics of theweed-control agents of this invention, that is, beneficial selectivityin pre-emergent application coupled with an extraordinary absence ofpost-emergent effects on standing crops. These characteristics make itfeasible to spray at moderate rates at or near planting time, followedby more drastic application at higher rates after the crop is standing,to prevent emergence of Weeds until after the crop has grown enoughfoliage to shade out other plant growth. In using this system of weedcontrol, the second application may be done by aerial spraying, so thatit is not necessary to enter the field to cultivate between planting andharvest.

I claim:

1. O dichloroacetyl-3,5-ditert.butyl-4-hydroxybenzaldoxime.

2. O-chloroacetyl 3,5 diterhbutyl-4-hydroxybenzaldoxime.

References Cited UNITED STATES PATENTS 1/1964 Horrom 260-566 AE 1/1965Koopman 260-566 AE U.S. Cl. X.R. Utility adequately classified in parentapplication,

HOW Pat. No. 3,503,732.

